CN109655821A - For determining the angular range of target, place and/or the radar method and radar system of speed - Google Patents

Abstract

The invention relates to a radar method for determining an angular orientation, a location and/or, in particular, a vector velocity of a target, wherein a first transmit-receive unit and at least one, in particular spatially separate from the first transmit-receive unit , the second transmit-receive unit is not synchronized, however, the measurement of the first transmit-receive unit and the second transmit-receive unit is triggered wirelessly or wiredly with a time offset Δt _n begins, wherein each Measurements of the sender-receiver unit. The invention also relates to a radar system for determining an angular orientation, a location and/or in particular a velocity of a vector, a radar method and/or use of the radar system for a mobile device, and a mobile device.

Description

Radar method and radar for determining angular bearing, location and/or velocity of a target system

technical field

The invention relates to a radar method and a radar system for determining the angular orientation, position and/or in particular the velocity of a vector of a target.

Background technique

Known radar methods, in particular for estimating vector velocities (cf. [1]-[3]), use distributed radar devices that measure the multiplicity of objects (targets) individually and independently of each other. Puller speed. The Doppler velocity can be interpreted as a projection of the vector velocity of the connection vector between the radar and the target. If the positions of the radar and the target are known or can be determined, vector velocities can be determined from the individual projections by solving a system of linear equations. However, the accuracy of this method is highly dependent on the geometric distribution of the station relative to the target ("precision factor").

A further possibility for radar measurements, in particular for determining vector velocities, consists in evaluating the difference in the phase characteristic curves between the two antennas (cf. [4]-[11]). This method enables higher accuracy and is less related to geometric problems. However, in the prior art according to [4]-[7], only the case where the target is in 0° azimuth (boresight) and in the far field of the array is dealt with. The publications [8]-[11] also deal with the case of azimuth ≠ 0°, but not the case of the near field of the array. The prior art methods according to [4]-[11] involving differences in the phase characteristic use two antennas which are connected to the radar device.

Since a relatively large aperture is required for accurate measurement of tangential velocity, the situation where the target is not in 0° azimuth and/or in the near field is of great interest.

[1] D.Kellner, M.Barjenbruch, K.Dietmayer, J.Klappstein, and J.Dickmann, "Instantaneous lateral velocity estimation of a vehicle using doppler radar," in Information Fusion (FUSION), 2013 16th International Conference on, 2013, pp. 877-884.

[2] H.Rohling, F.Folster, and H.Ritter, "Lateral velocity estimation for automotive radar applications," (lateral velocity estimation for automotive radar applications) in 2007IETInt.Conf.on Radar Systems (2007 International Conference on Radar Systems IET ), Edinburgh, UK, 2007 (Edinburgh, UK, 2007), pp. 181-181.

[3]W.Montlouis and P.-R.J.Cornely,"Direction of Arrival and AngularVelocity(DOAV)Estimation using Minimum Variance Beamforming,"(Using Minimum Variance Beamforming to Estimate Direction of Arrival and Angular Velocity (DOAV)) in Radar Conference, 2007IEEE, 2007 (In Radar Conference, 2007IEEE, 2007), pp. 641-646.

[4] A.W.Doerry, "Patch diameter limitation due to high chirp rates in focused SAR images," IEEE transactions on aerospace and electronic systems System), vol.30, no.4, pp.1125-1129, 1994 (Vol. 30, No. 4, pp. 1125-1129, 1994).

[5] A. Doerry, "Tangential Velocity Measurement using Interferometric MTI Radar," (Tangential Velocity Measurement using Interferometric MTI Radar) 2002. [Online]. Available (2002, online, available): http://prod .sandia.gov/techlib/access-control.cgi/2002/023614.pdf. [Accessed Sep. 26, 2017] (Accessed September 26, 2017)

[6] A. Doerry, B. Mileshosky, and D. Bickel, "Tangential velocity measurement using interferometric MTI radar," U.S. Patent 6 982 668B1, Jan. 3, 2006 ( US Patent 6 982 668 B1, January 3, 2006).

[7] J.A.Nanzer, "Millimeter-Wave Interferometric Angular VelocityDetection," (Angular Velocity Detection of Millimeter-Wave Interferometric Measurement) IEEE Transactions on Microwave Theoryand Techniques, Dec.2010 (IEEE Journal of Microwave Theory and Technology, December 2010).

[8] J.A.Nanzer and A.H.Zai, "Correction of frequency uncertainty inwide field of view interferometric angular velocity measurements," (correction of frequency uncertainty in wide field of view interferometric angular velocity measurements) in Microwave Symposium Digest (MTT) , 2012 IEEE MTT-S International, 2012, pp.1-3 (Microwave Symposium Digest (MTT), 2012 IEEE MTT-S International, 2012, pp. 1-3).

[9] J.A.Nanzer, K.Kammerman, and K.S.Zilevu, "A 29.5GHz radarinterferometer for measuring the angular velocity of moving objects," in Microwave Symposium Digest (IMS ), 2013 IEEE MTT-S International, 2013, pp. 1-3 (Microwave Symposium Digest (IMS), 2013 IEEE MTT-S International, 2013, pp. 1-3).

[10] J.A.Nanzer, "Resolution of interferometric angular velocity measurements," in Antennas and Propagation (APSURSI), 2011 IEEE International Symposium on, 2011, pp.3229-3232 (Antenna and Propagation (APSURSI) ), 2011 IEEE International Symposium, 2011, pp. 3229-3232).

[11] J.A.Nanzer, "Micro-motion signatures in radar angular velocity measurements," (Micro-motion signatures in radar angular velocity measurements) in Radar Conference (RadarConf) 2016IEEE, 2016, pp.1-4 (in 2016 Radar Conference (RadarConf) ), IEEE, 2016, pp. 1-4).

[12] T.Wagner, R.Feger, and A.Stelzer, "Wide-band range-Doppler processing for FMCW systems," (Wide-band range-Doppler processing for FMCW systems) in Radar Conference (EuRAD), 2013European, 2013, pp.160-163 (2013 Radar Conference (EuRAD), 2013 Europe, 2013, pp. 160-163).

SUMMARY OF THE INVENTION

It is an object of the present invention to determine the angular orientation, location and/or in particular the velocity of a vector of an object in the simplest possible manner and with relatively high accuracy.

The object is achieved with the features of claim 1 .

In particular, the object is achieved by a radar method for determining the angular orientation, location and/or in particular the velocity of a vector of a target, wherein the first transmitter-receiver unit and at least one (in particular spatially related to the first transmitter) - the second transmit-receive unit separate from the receive unit is not synchronized, however, the triggering of the first transmit-receive unit and the second transmit-receive unit with a time offset (trigger-offset time) Δt _n Measurement starts. Preferably, the measurements of each transmit-receive unit are processed in association.

If the time offset (trigger-offset time) between the first and second transmit-receive unit is greater than 1 ps, preferably greater than 1 ns, if necessary greater than 10 ns, then the second transmit-receive unit shall be considered to be different from the first transmit-receive unit - The receiving unit is out of sync. However, the time deviation Δt _n can optionally be ≦10 μs, preferably ≦1 μs (especially in the case of dynamic targets). Especially in the case of stationary targets, the time offset can also be larger. Correlation processing can in particular be understood to mean that the measurements of the individual transmit-receive units are further processed as if they were generated by a common local oscillator. An example of this is the two receive antennas of a SIMO radar.

As a result, the target can be detected in a simple manner, in particular the angular orientation, the location and/or the preferred vector velocity of the target can be determined. In particular, the present invention enables simple and accurate estimation (determination) of the vector velocity even in the case of azimuth ≠ 0° and/or in the near field. In addition, coarsely synchronized distributed radar stations can be used to generate large apertures.

The time offset (trigger-offset time) Δt _n is to be understood in particular as a time offset which arises depending on the method or system, in particular due to the use of wireless and/or wired transmission. The time deviation Δt _n is therefore inherent to the method or system in particular. Preferably, the measurements (and/or transmission signals) of the individual transmit-receive units are not generated by a common local oscillator.

At least two measurement signals, which are reflected by a common target, preferably interfere with each other, in particular by complex conjugate multiplication, especially in the time domain (=non-exclusive alternative a)). It should be noted here that complex conjugate multiplication can correspond to division by complex pointers with normalized magnitude.

Alternatively or additionally, the compressed, in particular range-Doppler compressed signals can interfere with each other, preferably by convolution, in particular in the frequency domain (=non-exclusive alternative b)).

The holographic processing is preferably carried out in the xy direction. The interference is preferably carried out along the Doppler direction, eg by multiplication in the time domain (alternative a)) or by convolution in the frequency domain (alternative b)). Holography can be provided as a basis for interference both in a) and b).

In particular, (alternatively or additionally) at least two signals are enabled to interfere holographically first in space, for example in a Cartesian x,y-coordinate system, and then pass in the Doppler plane (velocity plane) in the time domain Multiplication of (alternative a), especially by conjugate complex multiplication, or by convolution in the frequency domain (alternative b) interference.

Preferably, the vector velocity of the target is determined from the derived signal.

In principle, the method is particularly preferably configured such that the (2D or 3D-) vector velocity of the target can be determined.

Preferably, the first and/or second transmit-receive unit determines its own (vector) velocity (self-motion estimation) based on the (vector) velocity of one or more objects (eg stationary objects) with known (vector) velocity .

In a first alternative, the target can be in the near field. Alternatively, the target can also be in the far field. The near field should preferably be understood as the distance of the target which is less than or equal to the distance between two transmitter-receiver units (or in the case of multiple transmitter-receiver units, the two transmitters that are farthest from each other) - 10 times the spacing between the receiving units, or less than or equal to 10 times the aperture size of the system consisting of the transmitting-receiving units. In particular, the far field is understood to be the distance of the target which exceeds the just-mentioned relative value. Particularly preferably, the target is in the near field. Especially in the near field (in contrast to the prior art) precise measurements can be achieved in a simple manner.

In a specific implementation form, each transmit-receive unit forms a distributed aperture. The spacing between multiple transmit-receive units can be at least 20 cm, more preferably at least 50 cm, more preferably at least 100 cm (in the case of multiple transmit-receive units, this can apply to each next transmit - the spacing of the receiving units or, alternatively, the spacing between the two transmitting-receiving units which have the greatest distance from each other among all possible pairs of transmitting-receiving units).

The positioning of the target is preferably carried out according to the holographic principle.

In a specific embodiment, the method is an FMCW radar method (where FMCW stands for Frequency Modulated Continuous Wave).

Preferably, the method works according to the range-Doppler principle.

In a specific implementation form, the at least two transmit-receive units are single-station. The spacing between the individual transmit-receive units is preferably at least 5 times, more preferably at least 10 times the corresponding spacing between the transmit and receive antennas of the same transmit-receive unit (hereinafter also referred to as Rx antenna= receive antenna, or Tx antenna = transmit antenna).

Especially after holographic interference, the Fourier transform proceeds along a slow time. "Slow time" is defined in more detail below. Peak searches can be performed to determine elliptic/hyperbolic velocities, especially in multiple or all pixels (of the target). Furthermore, the determination of the elliptic/hyperbolic parameters can especially be performed in several or all pixels (of the target). Alternatively or additionally, a transformation of elliptic/hyperbolic velocity to (Cartesian) vector velocity can be performed.

The signal frequency can be halved before interference is formed.

The Doppler velocity can be determined, in particular for at least partially compensating for the Doppler shift.

An optimal filtering method can be used, especially for at least partially compensating for the Doppler shift and/or for relatively high radar bandwidths and/or relatively high target velocities.

Range-Doppler compression can be performed by means of a fractional Fourier transform (FRFT), especially with relatively high radar bandwidths and/or relatively high target velocities.

One or more (range-Doppler) compressed signals can be additionally compressed in the azimuth direction, preferably by means of Fourier transform and/or digital beamforming algorithms, in particular for side lobes inhibition.

In an embodiment, a method is proposed in which at least three transmit-receive units are used, preferably a 3D velocity determination is carried out, in particular by forming the intersection of two pairs, each consisting of an ellipsoid and a hyperboloid. Alternatively or additionally, an optimal filtering method can be used in which hypotheses are formed for multiple or all [ _x ,y, _z ,vx, _vy ,vz] combinations in the search area and combined with the measurements data for comparison.

According to an embodiment, the following method is proposed, wherein:

A first signal is generated in the first transmit-receive unit and transmitted, in particular radiated, via a path,

A further first signal is generated in the second transmit-receive unit and transmitted, in particular radiated, via the path,

a first comparison signal is formed by the first signal of the first transmit-receive unit and by such a first signal received by the second transmit-receive unit via the path, and

A further comparison signal is formed by the first signal of the second transmit-receive unit and by such a first signal received by the first transmit-receive unit via the path,

Preferably, the further comparison signal is transmitted, in particular communicated, from the second transmit-receive unit to the first transmit-receive unit, and/or

Wherein, a comparison-comparison signal is preferably formed from the first comparison signal and the further comparison signal, and/or

In this case, in a first step, deviations of the respective comparison signals caused by systematic deviations in the respective transmitting-receiving units are compensated, and in a second step, the first comparison signal of the two comparison signals or the The at least one complex value formed by the signal derived from the comparison signal is used to adjust at least one complex value of the second comparison signal of the two comparison signals or the value of the signal derived from the second comparison signal, thereby forming the adjustment signal, wherein , adjusted such that a complex-valued vector sum or difference or a complex-valued phase sum or difference is formed by mathematical operations. Modifications of this method (also referred to below as method I and method II) can be derived from DE 10 2014 104 273 A1 and/or WO 2017/118621 A1. Accordingly, the relevant disclosures of DE 10 2014 104 273 A1 and/or WO 2017/118621 A1 are expressly incorporated by reference into the present invention. A corresponding radar system is also described in DE 10 2014 104 273 A1. The method according to DE 10 2014 104 273 A1 shall hereinafter be referred to as "method I". The configuration of the radar system according to DE 10 2014 104 273 A1 shall be referred to as "configuration I". Another approach and another configuration of a radar system for increasing correlation can be derived from WO 2017/118621 A1. The methods or radar systems described in these two applications shall hereinafter be referred to as "Method II" and "Configuration II". According to methods I and/or II, the method is preferably applied to direct paths and cross paths.

The above-mentioned objects are also achieved by a radar system for determining the angular orientation, position and/or in particular the velocity of a vector of a target, in particular for carrying out the above-mentioned method, the radar system is provided with a first transmitting-receiving unit and at least one second transmitting- a receiving unit, the first transmitting-receiving unit and the second transmitting-receiving unit being asynchronous to each other, provided with control means configured to wirelessly or _wiredly Triggering the start of measurements of the first transmit-receive unit and of the second transmit-receive unit, provided with calculation and/or evaluation means configured such that the measurements of the transmit-receive unit are processed in association .

As long as calculations, evaluations or other method steps are carried out (eg in the (corresponding) transmit-receive unit), it also includes, if necessary, a physically separate evaluation device, which is connected to one or more transmit-receive units superior. Furthermore, the control device, for example to trigger the start of the measurement, can be designed as a physically separate control device (if necessary in a common component with the evaluation device, in particular a housing), which is connected to one or more on the send-receive unit. For example, a corresponding transmit-receive unit can be formed as a device which consists of, in particular, one or more antennas with some (several) signal-generating or signal-processing components, while other components such as a signal comparison unit or a control unit And/or the evaluation device can be connected to such a device as a structurally independent component. Wherever components are used, said components (as far as technically feasible) can be constituted as so-called hardware consisting of components for processing and/or converted into signal or data processing steps which are executed entirely or partly in a processor.

In general, the control and/or evaluation device can be part of one or more transmit-receive units or be connected to one or more such transmit-receive units. If necessary, a physically separate control and/or evaluation device can be provided, which is connected to the corresponding transmitter-receiver unit or to other components of the corresponding transmitter-receiver unit. Alternatively, the control and/or evaluation device can optionally be integrated into the first and/or second (usually additional) transmitter-receiver device, for example in a common housing and/or as a structural unit.

Each transmit-receive unit can have one or more transmit-receive antennas.

The above-mentioned objects are also achieved by the use of a method of the above-mentioned type and/or a system of the above-mentioned type for a mobile device, preferably a vehicle, in particular a passenger car and/or a truck.

The above-mentioned objects are also achieved by a mobile device, preferably a vehicle, especially a car and/or a truck, comprising the above-mentioned system.

Description of drawings

In the following description, further bases, aspects and embodiments of the invention are also described with reference to the drawings. here:

Figure 1 shows two receiving units spaced apart from each other;

Figure 2 shows two receiving units in a different configuration from Figure 1;

Figure 3 shows a view of the motion of a target in the near field;

Figure 4 shows the resulting 3D spectrum for estimating velocity;

Figure 5 shows a measurement with two cars;

FIG. 6 shows a measurement with four cars and one pedestrian.

Detailed ways

In the following description, the same reference numerals are used for the same and the same functions.

Associated processing of distributed radar stations for positioning :

Transmit signals of FMCW radars operating according to the range-Doppler principle and receive signal The phase of can usually be described as

and

in:

-t _f = 0...T = tt _i : "fast time" or "fast time"; T is the scan duration, t is the absolute time.

-t _i = iT: "slow time" or "slow time", i=0...M is the number of scans, M is the number of ramps in the burst.

- The "time of flight" from the Tx antenna to the target and back to the Rx antenna; d _rt (t _f ,t _i ) is the corresponding separation (see (4)).

-f ₀ : carrier frequency; Sweep slope; B: bandwidth; c: propagation speed.

- Unknown initial phase of the scan.

- The reflected phase of the target.

Thus, the phase of the (baseband) signal resulting from mixing the Rx signal (received signal) with the Tx signal (transmitted signal) is

with round-trip spacing

Here, d _rt,0 represents the round-trip distance to the target at the beginning of the transient burst, and ν _r represents the radial velocity of the target relative to the radar. Substituting (4) into (3) ignoring terms containing t _f ² , t _i ² and t _f t _i yields

The phase of the signal obtained in (5) is only related to the distance to the target, the relative radial velocity of the target and the reflection phase of the target. Unknown initial phase disappeared during the mixing process of (3).

If N distributed radar stations (transmit-receive units) are used, whose clocks are not frequency-synchronized, but of the same type, for which distributed radar stations are triggered simultaneously with accuracy Δt _n via wired or wireless means The measurements are started and their slopes are displaced from each other by a frequency offset _Δfn , the following signal model is obtained for the baseband signal phase in the radar number n:

The individual phase terms have the following meanings:

- Phase offset terms, which are related to path differences between stations and can be used for angle estimation.

- Frequency proportional to spacing. Produced by compression in the "fast time" direction (eg by means of FFT).

- frequency, which is proportional to radial velocity. Produced by compression (eg by means of FFT) in the "slow time" direction.

- Phase term, which is approximately equal in each station n, provided that the reflection characteristics of the target are the same in each direction illuminated by the radar.

Because the trigger-offset time Δt _n ≈ 15 ns (if necessary 0.1 to 100 ns, especially 5 to 30 ns) in the wired case, and Δt _n ≈ 1 μs (if necessary 0.1 to 10 μs, especially 0.5 ns) in the case of wireless triggering to 2 μs), in general, |ν|Δt _n ≈ 0, meaning that the target position remains approximately constant during the time Δt _n .

It is therefore only relevant for the distance between the respective radar and target and can be processed in relation to all stations. Each radar forms a distributed aperture.

For signal s _n in station n after distance-compression (compression along fast time t _f ):

Here, W _d represents the Fourier transform of the window function used in the distance. Starting from this signal model, a 2D localization of the target can be performed according to the holographic principle with the aid of the following optimal filters:

Has assumptions about round-trip spacing

P _Tx,n or P _Rx,n is the known 2D position of the Tx or Rx antenna of radar n. Each radar (transmit-receive unit) may have one or more Tx or Rx antennas. If there is more than 1 antenna, then a separate hypothesis must be created for each Tx-Rx combination according to the same principle. P _t,hyp is the hypothesis to be detected for the 2D position of the target. If the coordinates in (9) are replaced by 3D coordinates, the method can be adapted directly to 3D.

The probability that the target is at the position P _t,hyp is then calculated as follows:

If the target is located in the far field of the aperture, (10) for the beamforming method is reduced and the 2D search for x and y can be replaced by a 1D search for spacing followed by a search for angle .

If the target is in the near field of the aperture, then preferably a 2D search can be performed according to (10). Since the targets can lie in different distance ranges (“range migration”) in the individual radars, an interpolation method in the distance direction may be necessary, which can be implemented as a complex-valued linear interpolation method.

This method allows for associative processing of unsynchronized distributed radar stations, which enables large apertures. As a result, the target can be positioned with high precision.

Correlation of Distributed Radar Stations to Determine Vector Target Velocities in the Far Field

FIG. 1 shows two transmit-receive units 1 , 2 spaced apart from each other by a distance b ₁ , which transmit-receive units measure almost simultaneously with a target according to the FMCW-range-Doppler principle, said target being measured in a vector Velocity v movement.

If the target is in the far field of an antenna array comprising transmit-receive units 1 , 2 (and if necessary further transmit-receive units), the geometry can be as shown in FIG. 1 . The target is initially [d ₀ , θ ₀ ] in radar polar coordinates and moves with a vector velocity ν. The change in spacing (radial component) between the radar and the target can be described as:

d(t)=d ₀ +v _r t (11)

has a radial velocity ν _r . The angular change (tangential component) is

Here, ω represents the angular velocity, and ν _t represents the tangential velocity. After range compression (eg by means of a Fourier transform), the relevant signal model in the transmit-receive units 1, 2 operating according to the FMCW range-Doppler principle is:

where W _d represents the Fourier transform of the window function used within the distance. Here, _ti denotes the start time of the FMCW ramp ("slow time" or "slow time"). Due to the far-field approximation d ₀ >>b ₁ , d ₁ ≈d ₂ =d ₀ applies for the distance to the target measured in both radars, resulting from the interference of the two signals:

where |·| ^* denotes complex conjugation. By approximating ω _a t _i ≈0 and by Taylor sequence expansion, (14) can be approximated as

The subsequent Fourier transform along _ti yields:

Here, f _a denotes the frequency of the signal generated in the image range (azimuth direction). The angular velocity ω _a / tangential velocity ν _t is then obtained as:

where f _a,max denotes the position of the maximum value in the 2D spectrum s(d, 2πf _a ) along the f _a direction (azimuthal direction in the image range).

Interference simulation (14) can also be applied to range-Doppler compressed data. The multiplication in (14) must then be replaced by convolution.

The complete velocity vector can be determined by estimating ν _r by means of the standard-range-Doppler method and the tangential velocity ν _t orthogonal to this in (17). This presupposes knowing the angle θ ₀ relative to the target. The angle can be determined, for example, by means of known angle estimation techniques (beamforming).

Resolution and Uniqueness Range

The resolution of the tangential velocity estimate for the rectangular window can be obtained by substituting in (17) to calculate

(For Hann windows, the resolution ≈ 2 times lower.)

By substituting in (17) For the uniqueness range can be derived

Therefore, both resolution and uniqueness range are related to the spacing and angle relative to the target. _An increase in aperture b1 results in an improvement in resolution and a reduction in the range of uniqueness. This leads to an increase in the range of uniqueness if there are further receiver units between the two existing receiver units.

A common solution for associative processing of distributed radar stations for determining vector target velocities (also in the near field middle)

The prerequisite is at least two roughly synchronized radar units (transmit-receive units). The spacing between the cells is b ₁ (see FIG. 2 ; FIG. 2 shows two transmit-receive units spaced from each other by the spacing b ₁ , which transmit-receive units are connected to the target according to the FMCW range-Doppler principle almost simultaneously measured). The two radar units are quasi-monostatic (corresponding spacing between Rx and Tx <<b ₁ ). For the distance to the target it does not necessarily apply that d ₀ >>b ₁ , meaning that the target can be in the near field.

In this case, the signal model according to the FMCW range-Doppler measurement principle can be expressed after range compression as:

d _rt,n (t _i ) describes the Doppler path spacing from the radar Tx antenna to the target and back to the Rx antenna:

P _Tx,n /P _Rx,n is here the 2D position of the Tx/Rx antenna of radar unit n. P _t is the position of the target in 2D. ||·|| represents the Euclidean norm. For t _i =0 d _rt,0,n =d _rt,n (0) applies.

Figure 1 shows a view of a target as a movement along an ellipse/hyperbolic curve in the near field of a dual radar unit arrangement. As can be seen from the geometry in Figure 3, the position of the target can be determined by the intersection of the ellipse and the hyperbola, where the two radars are in focus. The ellipse is described by the following parameters

and the hyperbola passes through

to describe. The resulting elliptic/hyperbolic equation is

oval: in, and

hyperbola: in,

The intersection of the ellipse and the hyperbola [x0,y0] (strictly speaking, there are two intersections, however one can be easily chosen by rationality considerations, the other is located behind the radar unit) as

For a moving target, x=x ₀ +ν _x t _i is obtained, and y=y ₀ +ν _y t _i , and then a _E (t _i ) and a _H (t _i ) (these linear equations apply to the case || ν||<<d _rt , where T is the FMCW ramp duration).

Direct interference of the two signals may not be feasible here, since d _rt,0.1 ≠d _rt,0.2 (“distance shift”). Instead of this, it is preferable to follow the holographic interference method:

in,

Here, P _t,hyp is the hypothesis for the target position in 2D. If the two signals are made to interfere without complex conjugation, then one obtains

The target motion can thus be interpreted as the motion a E(t i ) from ellipse to ellipse along the hyperbola corresponding to the radial velocity, and as the movement a _E (t _i ) along the ellipse corresponding to the tangential velocity from the hyperbola to the hyperbola perpendicular to it. the motion a _H (t _i ) (see Figure 3).

The Fourier transform along _ti following this yields:

The result of this transformation is shown in FIG. 4 . Figure 4 shows the 3D spectrum used to estimate the resulting tangential/radial velocities given x and y. The two spectra have the same shape, but are located at different locations along the z-axis.

Searching for a maximum along the _ωΔ or _ωΣ direction in the resulting 3D spectrum provides

and

By means of the partial derivatives of (26) and (32), the components of the velocity vector can be calculated as

and

and

Then, the velocity vector in the Cartesian coordinate system is

get unique range

The phase addition in (29) results in a doubling of the measured Doppler frequency, which results in a halving of the unique measurement range. This can preferably be avoided by halving the signal frequency before the interference is formed. For a generic signal s(t)=Aexp(jφ(t)) in analytical form, the signal can be expressed as

(Frequency scaling property of the Fourier transform). Thus, the range of uniqueness in the Doppler direction can be obtained at least substantially completely.

Compensate for Doppler shift

The Doppler shift can preferably be compensated for by determining the Doppler velocity for each target and thus correcting the spacing. Alternatively, an optimal filtering method similar to [12] can be followed. Then, the algorithm presented in the present invention can be applied preferably unchanged to the result.

high bandwidth or high speed

If the radar has a high bandwidth or the target is moving so fast that the approximation is no longer satisfied Then FFT-based Doppler compression may no longer be applicable, since the spacing to the target changes significantly from ramp to ramp during the transient burst.

This case can also be covered with the aid of an optimal filtering method similar to [12]. Alternatively, range-Doppler compression can be performed by means of a fractional Fourier transform (FRFT). The algorithm presented in this invention can then be applied unchanged to the result.

Sidelobe suppression

If both radar units have two or more antennas, the range-Doppler compressed signal can be additionally compressed in the azimuth direction by means of Fourier transform or digital beamforming algorithms (Bartlett, Capon, MUSIC, etc.) . The presented method can then be applied invariantly to the results. This causes sidelobe suppression in the resulting [ _x , _y ,νx,νy] image.

Assignment of targets to each other in the 3D spectrum for radial and tangential velocities

In the case of more than one target in the spatial resolution unit, the targets can be separated from each other in terms of amplitude, since the signal originating from one target has the same amplitude A ₁₂ in both frequency spectra, but different frequencies and phase (see equations (30) and (31) and Figure 4). If there are two or more targets with the same magnitude in the spatial resolution unit, target separation can be accomplished by means of a subsequent tracking algorithm.

Expansion to 3D/2 or more radar stations

A 3D vector velocity estimation of the target can be achieved by means of at least three spatially positioned radar units (transmit-receive units). The result is produced by the intersection of two pairs consisting of an ellipsoid and a hyperboloid.

The method can generally be extended to any number of transmit-receive units and radar devices, especially if optimal filters are used instead of Fourier transform processing. For this method, a hypothesis is formed for each combination of [ _x , _y , _z ,νx,νy,νz] in the search area and compared to the measured data. For a target at a hypothetical position P _hyp = [x _hyp , y _hyp , z _hyp ] and a radar number _n at position pn, the separation between radar n and target d _n (x _hyp , y _hyp , z _hyp ) and the unit vector ν _n (x _hyp , y _hyp , z _hyp ) from the radar to the target can be calculated as

For the measurement signal s _n (d,t _i ) in radar n according to the FMCW range-Doppler principle, the following optimal filters can be listed

With assumptions for radial velocities ν _r,hyp,n (ν _x,hyp ,ν _y,hyp ,ν _z,hyp ) (Doppler velocities):

|· Here represents the scalar product of two vectors. The result is thus calculated as

It has the number of radar units N _rad and the number of FMCW scans N _sw . By searching for the maximum value in the resulting 4D pseudospectrum, the target position and vector velocity can be determined. For 3D problems, the 6D spectrum is obtained in a similar manner.

The method may be computationally more cumbersome than previously proposed FFT-based methods.

Application of the method to direct and cross paths obtained according to methods I and/or II

If two radars measure relative to the target according to methods I and/or II, two direct measurement paths are obtained (d _rt,11 =2d ₁ : radar1→target→radar1,d _rt,22 = _2d2 : radar 2→target→radar2) and two cross paths ( _drt,12 =d1 _{+ d2} : radar1→target→radar2, _{drt,21 = d2} +d1: radar2→target→radar1 ). Since methods I and/or II enable phase-correlated evaluation of each cross-path, they can also be processed according to the described method to estimate vector velocities.

If the hyperbolic and elliptic parameters in equations (22) and (23) are expressed by d _rt,11 and d _rt,21 , then one obtains

and

Therefore, the method can also be applied invariably to a combination consisting of a direct path and a cross path. This has the advantage of being able to see objects that are visible in the cross path and in one direct path, but not in both direct paths.

Application example for vector velocity estimation according to the proposed method

FIG. 5 shows an application in the automotive sector with a motor vehicle ( 20 ) equipped with two radars ( 1 ), ( 2 ) which are triggered almost simultaneously by a signal. Another vehicle (30) travels in the direction of arrow (4).

The car ( 20 ) can, for example, wait at the intersection or drive to the intersection. By means of standard processing of radar data on the car (20), the distance and angle to the car (30) can be determined. Furthermore, relative radial velocities can be determined. Since in this case the car (30) moves approximately tangentially to the connecting axis between the radars (1), (2) and the target, ie the car (30), the Doppler frequency will be ≈0 Hz. The measured radial velocity will therefore be ≈0 m/s. Therefore, it cannot be determined whether the car (30) is running or parked. By means of the method proposed according to the invention, the signals of the radar stations (1), (2) can be processed in association, although the radar stations are not (phase) synchronized, and the (complete) of the vehicle (30) can be determined therefrom. Vector speed. The information can be fused with other algorithms for environment detection, which is beneficial for driver assistance systems and automated driving. With this method, if necessary in combination with existing methods, it is possible to assign amplitude (power), velocity and direction of motion to each point in the radar image.

FIG. 6 shows another application with a car ( 20 ) equipped with two radars ( 1 ), ( 2 ), which are triggered almost simultaneously by a signal, and the car travels in the direction of the arrow ( 4 ) . There is a parked car (30) on the side of the road. The pedestrian (5) is traveling on the road in the direction of the arrow (6).

If the car (20) is moving in the direction of the arrow (4) and there is a parked car (30) on the side of the road, the car (20) may not recognize the pedestrian (5) moving in the direction of the arrow (6) until the last moment, which This is because pedestrians may be obscured by parked cars. Once the radar is able to see the pedestrian, additionally measuring the tangential velocity enables a faster response and prevents possible accidents.

All in all, the invention also includes particularly accurate estimation of the (2D or 3D) vector velocity of an object (target). For this purpose, at least two (spatially separated) FMCW radars can be provided which measure in particular according to the range-Doppler principle. These FMCW radars are preferably only roughly time synchronized. Both stations are capable of (approximately) simultaneously triggering and transmitting and receiving FMCW bursts (with known frequency offsets from each other). The full vector velocity of the object (target) in the surrounding environment can then be estimated from the interference of the resulting (baseband) signal.

At this point it is pointed out that all the components or functions described above, individually or in any combination, in particular the details shown in the figures, are claimed as essential to the invention. Variations from this are familiar to those skilled in the art.

Claims (15)

1. A radar method for determining the angular orientation, location and/or - in particular vectorial - velocity of a target, wherein a first transmit-receive unit (1) and at least one - in particular spatially A transmitter-receiver unit is separated - the second transmitter-receiver unit (2) is not synchronized, however, the first transmitter-receiver unit (1) and the second transmitter are triggered wirelessly or wired with a time offset Δt _n - Start of the measurements of the receiving unit (2), wherein the measurements of the respective sending-receiving units (1, 2) are processed in association. 2. The method of claim 1, wherein, a) Interfering at least two measurement signals reflected by a common target with each other, in particular by complex conjugate multiplication, and/or b) causing the range-Doppler compressed signals to interfere with each other, especially by convolution, and/or c) Performing holography, in particular in the xy direction and interferometry in the Doppler direction. 3. The method of claim 2, wherein the vector velocity of the target is determined from the derived signal. 4. The method of one of the preceding claims, wherein the target is in the near field, or alternatively the target is in the far field. 5. The method according to one of the preceding claims, wherein each transmit-receive unit (1, 2) forms a distributed aperture. 6. The method according to one of the preceding claims, wherein the positioning of the target is carried out according to the principle of holography. 7. The method according to one of the preceding claims, wherein the method is an FMCW radar method, and/or a method operating according to the range-Doppler principle. 8. The method according to one of the preceding claims, wherein the at least two transmit-receive units (1, 2) are single-station. 9. The method according to one of the preceding claims, wherein, in particular in alternative c) of claim 2, a Fourier transformation is performed, preferably along slow time, and/or - especially in multiple or all pixels - perform a peak search to determine elliptic/hyperbolic velocities, And/or - in particular in several or all pixels - a determination of elliptic/hyperbolic parameters and/or a transformation of said elliptic/hyperbolic velocity into a - preferably Cartesian - vector velocity is performed. 10. The method according to one of the preceding claims, wherein the signal frequency is halved before forming the interference, and/or the Doppler velocity is determined, in particular for at least partially compensating for the Doppler shift, and/or Or use an optimal filtering method, especially for at least partially compensating for Doppler shifts and/or for relatively high radar bandwidths and/or relatively high target velocities, and/or by means of fractional Fourier The Leaf Transform (FRFT) performs range-Doppler compression, especially at relatively high radar bandwidths and/or relatively high target velocities, and/or converts one or more - if necessary range-Doppler Compressed—The signal is additionally compressed in the azimuthal direction, preferably by means of a Fourier transform and/or a digital beamforming algorithm, especially for sidelobe suppression. 11. The method according to one of the preceding claims, wherein at least three transmit-receive units are used, wherein a 3D velocity determination is preferably carried out, in particular by forming two pairs of intersections, the two pairs being formed by an ellipsoid and a double, respectively. Surface formation, and/or use of optimal filtering, where hypotheses are formed for multiple or all [ _x ,y, _z ,vx, _vy ,vz] combinations in the search area and the hypotheses are combined with the measurement data Compare. 12. The method of one of the preceding claims, wherein, A first signal is generated in the first transmit-receive unit (1) and transmitted, in particular radiated, via the path, A further first signal is generated in the second transmit-receive unit (2) and transmitted, in particular radiated, via the path, forming a first comparison signal from said first signal of said first transmit-receive unit (1) and from such a first signal received by said second transmit-receive unit (2) via said path, and A further comparison signal is formed by said first signal of said second transmit-receive unit (2) and by such a first signal received by said first transmit-receive unit (1) via said path, Thereby, the further comparison signal is preferably transmitted from the second transmit-receive unit (2) to, in particular communicated to, the first transmit-receive unit (1), and/or Wherein, a comparison-comparison signal is preferably formed from the first comparison signal and the further comparison signal, and/or Wherein, in a first step, deviations of the respective comparison signals caused by systematic deviations in the respective transmit-receive units are compensated, and in a second step, the first comparison signal of the two comparison signals or the At least one complex value formed by a signal derived from a comparison signal is used to adjust at least one complex value of a second comparison signal of the two comparison signals or a value of a signal derived from the second comparison signal, thereby forming an adjustment signal, Therein, the adjustment is made such that a complex-valued vector sum or difference or a complex-valued phase sum or difference is formed by mathematical operations. 13. A radar system for determining the angular orientation, location and/or - in particular vectorial - velocity of a target, in particular for carrying out the method according to one of claims 1 to 12, wherein , is provided with a first sending-receiving unit (1) and at least one second sending-receiving unit (2), the first sending-receiving unit and the second sending-receiving unit are not synchronized with each other, and a control device is provided, so The control device is configured to trigger the measurement of the first transmit-receive unit (1) and the second transmit-receive unit (2) wirelessly or by wire with a time offset Δt _n starting with calculation and/or evaluation Means, the calculation and/or evaluation means are configured such that the measurements of the respective transmit-receive units (1, 2) are processed in association. 14. Use of the method according to one of claims 1 to 12 and/or of the system according to claim 13 for a mobile device, preferably a vehicle, in particular a passenger car and/or a truck. 15. A mobile device, in particular a vehicle, preferably a car and/or a truck, comprising a system according to claim 13.